The Astronomer's Proposal Tool (APT) is the tool used to design observing programs for the Nancy Grace Roman Space Telescope.

APT Overview

The Astronomers Proposal Tool (APT) has been in use as an observation planning tool for HST and JWST; it now includes options for the Roman Space Telescope. APT is a stand-alone GUI-based software package used by proposers to write, validate, and submit observing programs. APT runs on your local machine, but accesses various tools and databases over the internet for performing certain tasks.

In most of the parameter fields in the APT graphical interface, you choose a legal value from a list in a pull-down menu (or check a box). In a few other parameter fields you enter a free text value in the field using the formats specified in this document. If you haven’t selected or entered a legal value or value then required parameter fields are marked with a red X icon.

The APT user interface for a new Roman proposal, or an approved program. This particular image shows the Roman Demonstration Program 960. The APT version and filename are visible in the banner at top. When APT is first opened, a pull-down menu from the **New Roman Proposal** tab (upper left, under the top tool bar) allows a user to create a new Roman proposal. The left panel allows for several programs to be open at once. The time and data volume are calculated by APT as the program is built and displayed on this page.

Current Version of APT

APT is used for multiple missions in operations (both HST and JWST). APT support for the the Roman mission is under active development. APT is updated on a regular basis to reflect the most current knowledge of on-going missions and to reflect development status of the Roman mission. APT version 2025.8 is the most current release that has Roman features enabled. Documentation on the Roman APT User's Guide (RAUG) is up-to-date for this version. Changes to the technical details and other specifications presented here are expected as a part of pre-launch development. Therefore, specific technical implementations are subject to change. APT releases typically occur every three months.

Working with program files

These are common tasks associated with creating and managing .apt files:

To create a new Roman program, click New Roman Proposal in the File menu.

To save a draft program as a local .apt file, click Save or Save As... in the File menu.

To open a previously saved draft program, click Open... or Open Recent in the File menu.

To review a PDF format of the currently selected program, click PDF Preview on the APT tool bar.

To include your draft program in your RTPS submission, attach your completed .apt file.

Once a program is approved by the TAC:

To retrieve and open an approved program from STScI, in the File menu click Retrieve from STScI > Retrieve using Proposal ID, then enter the Program ID.

To send an update to an approved program to STScI, Submit the Program.

Demonstration programs

Demonstration programs are available from the APT File menu, which are designed to help new users create their first Roman survey. These demonstration programs include a range of observing types and strategies which can be easily modified for a wide range of targets and science cases. This includes miniature versions of the four Community Surveys, so that their pointings and observing strategies can be explored without the huge size of the full programs.

Demonstration programs have a status of Approved, so in order to start working on your own Draft program, change the status to Draft (click Reset to Draft on the Program Information Page).

The following demonstration programs are available with the following ID numbers and key attributes:

960: M33 imaging epochs (variable Pass Plans used across multiple epochs)
961: LMC spectroscopy (includes reference imaging, with both a large mosaic and small Region Target for comparison)
962: Spatial study of Omega Cen (imaging and spectroscopy of a crowded field)
963: Dwarf spheroidal galaxies (deep imaging and spectroscopy)
966: GPS Demo (miniature Galactic Plane Survey)
967: GBTDS Demo (miniature Galactic Bulge Time-Domain Survey)
968: HLTDS Demo (miniature High-Latitude Time-Domain Survey )
969: HLWAS Demo (miniature High-Latitude Wide-Area Survey)

Roman APT demonstration Program 961 (LMC): square mosaic, Region Planner using square mosaic as segment, Region Information (with coordinates), Aladin plot of region target overlayed on Digitized Sky Survey image of the Large Magellanic Cloud (LMC). Note that although the Region Planner has created 19 segments, the user has deselected 3 of the nearly-empty segments in the list of Region Coordinates.

Getting help

Documentation

The following guides and handbooks are available (direct links are available from the APT Help menu):

Roman APT User Guide
The Wide Field Instrument
Roman Data Handbook
Roman Simulation Tools
Roman Community Surveys
Roman Proposals Documentation, maintained by the Science Support Center (SSC) at IPAC.

Additional documentation for Roman is under development.

APT Roman Help menu

Direct links to assistance are available from the APT Help menu:

Download APT Link to download current version of APT for Roman.

Roman What's New Release notes for APT for Roman. Highlights changes and new features.

Roadmap Link to the Quick Start Guide, which is an overview of basic steps to build a Roman program.

Help Desk Link to the Roman APT Help Desk, where you can submit Roman Help Desk requests.

FAQ and Knowledge Base The Roman APT Knowledge Base contains FAQ-style information and tips.

Call for Proposals The Roman Call for Proposals main page

Roman APT User Guide Roman APT User Guide

Roman Simulation Tools Handbook Simulation Tools Handbook. Documentation for the tools and resources used to plan observations and simulate imaging data from the Roman Wide Field Instrument (WFI).

Roman WFI Imaging Mode User Guide The Wide Field Instrument

Roman WFI Exposure Time Calculator Roman WFI Exposure Time Calculator

Context-Sensitive Help

Context-Sensitive help is another form of assistance available with APT. If you hover the cursor over many of the parameter names in the APT graphical interface, a small "?" appears next to the cursor if documentation is available for that item. Clicking on the parameter name will open the relevant documentation in your browser.

Formatting in the Roman APT User Guide

Special formatting is used throughout the Roman APT User Guide to help identify specific aspects of APT as described in the table below. Additionally, hovering a cursor over the graphic associated with each type of formatting will provide the name of the formatting.

Roman APT User Guide Formatting Table

Example	Hover-text Name	Explanation
Parameter	APT Parameter Field	The name of a parameter in the APT tool.
Value	APT Value Field	A format marker for values in APT that require users to provide specific information by entering it in a text field.
Calculated	APT Calculated Output	A marker indicating that the value is calculated by the APT software. It's an output that users cannot edit in APT.
List	APT Legal Field	An indicator that users can select the specified option from a list provided in APT, typically in the form of a drop-down menu.
Range	APT Range Field	This is used to specify the allowed range of numerical values for a given parameter.
Restricted	APT Restricted Field	These are APT fields that users generally do not need to access, such as calibration specific fields.
Warning	APT Warning	Formatting denoting items which will cause an APT warning, also indicated in the APT software by a yellow triangle.
Error	APT Error	This formatting marks items which will cause an APT error, also indicated in the APT software by a red X.

APT errors and warnings

Warnings and Error messages generated by APT are intended to help users identify and resolve problems or inconsistencies. Hover the cursor over these icons for pop-up help with a short description. You can also get summaries of these messages by clicking the Errors and Warnings icon on the top tool bar or the “errors and warnings” box at bottom right in the GUI.

For additional questions not answered in this article, please contact the Roman Help Desk.

Latest Update	19 Dec 2025	Updated for APT version 2025.8 release
Publication	15 Dec 2022	Initial publication of the article.

Astronomers Proposal Tool (APT)